Device for high-resolution measurement of magnetic fields

• US 6,690,162 B1
• Filed: 11/16/2001
• Issued: 02/10/2004
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: Qest Quantenelektronische Systeme GmbH (Fritz Dräxlmaier Holding GmbH)
• Original Assignee: Qest Quantenelektronische Systeme
• Inventors: Oppenlaender, Joerg, Haeussler, Christoph, Schopohl, Nils
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): KINDER, DARRELL D
• Application Number:
  US09/857,269
• Time in Patent Office: 816 Days
• Field of Search: 324/248, 505/846, 327/528, 600/409, 259/31-34
• US Class Current: 324/248
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• CPC Class Codes: G01R 33/0354 SQUIDS
• CPC Class Codes: Y10S 505/846 using superconductive quantum interference device, i.e. squid

Abstract

A device is proposed for high-resolution measurement, in particular for high-resolution absolute measurement of magnetic fields, having a network (1) of transitions (3) between superconductors (5, 6) which exhibit Josephson effects, called junctions below, the network comprising closed meshes (7, 8, 9, 10, 11, 12, 13), denoted by cells below, which in each case have junctions (3), which junctions are connected in a superconducting fashion, and at least three of these cells being connected in a superconducting and/or nonsuperconducting fashion. The object of the invention consists in further developing this device in such a way that it is possible to make absolute measurements of magnetic fields in a highly sensitive fashion. This object is achieved by virtue of the fact that the junctions (3) of the at least three cells (7, 8, 9) can be energized in such a way that a time-variant voltage drops in each case across at least two junctions of a cell, the time average of which voltage does not vanish, and in that the at least three cells are configured differently geometrically in such a way that the magnetic fluxes enclosed by the cells in the case of an existing magnetic field differ from one another in such a way that the frequency spectrum of the voltage response function has no significant Φ₀-periodic component with reference to the magnetic flux.

Claims

1. A device for high-resolution measurement of magnetic fields, having a network of junctions between superconductors which exhibit Josephson effects, the network comprising a plurality of closed cells, each cell having at least two junctions connected in a superconducting fashion, wherein at least three of said cells are connected electrically and can be energized in such a way that a time-variant voltage drops across at least two junctions of each of said at least three cells, the time average of which voltage does not vanish, and wherein said at least three cells are configured differently geometrically in such a way that the magnetic fluxes enclosed by the cells in the case of an existing magnetic field differ from one another in such a way that a frequency spectrum of a voltage response function has no significant elementary-flux-quantum-periodic (Φ

₀-periodic) component with reference to the magnetic flux, and if a discrete frequency spectrum exists, the contribution of the Φ

₀-periodic component of the discrete frequency spectrum is not dominant by comparison with a non-Φ

₀-periodic component of the discrete frequency spectrum.

2. The device according to claim 1, wherein at least one cell of the network contains, in addition to at least two junctions across which there drops a time-variant voltage whose time average does not vanish, at least one further junction, which is not directly energized.

3. The device according to claim 1, wherein the at least three cells are configured differently geometrically in such a way that the magnetic fluxes enclosed by the cells in the case of an existing magnetic field are not in a rational ratio to one another.

4. The device according to claim 1, 2 or 3, wherein a plurality of cells form a network, in which all junctions are connected electrically in parallel such that the junctions can be energized in the same direction.

5. The device according to claim 1, 2 or 3, wherein a plurality of cells are connected electrically in series such that the junctions in the network can be energized in the same direction.

6. The device according to claim 4, wherein a plurality of said networks are connected electrically in series such that the junctions can be energized in the same direction.

7. The device according to claim 5, wherein a plurality of said networks are connected electrically in parallel such that the junctions can be energized in the same direction.

8. The device according to claim 1, wherein a plurality of said networks are connected electrically in parallel with the aid of superconducting twisted-pair cables in such a way that the junctions in the networks can be energized in the same direction.

9. The device according to claim 1, wherein the network is voltage-driven.

10. The device according to claim 1, wherein the network is current-driven.

11. The device according to claim 1, wherein the junctions are designed as point contacts.

12. The device according to claim 1, wherein the geometry of the arrangement of the cells is designed so as to reduce magnetic crosstalk between cells which is implied by a magnetic self-field produced by a current flowing in the cells.

13. The device according to claim 1, further comprising a superconducting loop arrangement fitted in such a way that the magnetic flux produced by a primary magnetic field in the superconducting loop arrangement is coupled into the cells of the network.

14. The device according to claim 1, wherein the cells of the network are aligned in a spatially differing fashion in such a way that at least two of three spatial field components of a primary magnetic field can induce a magnetic flux in the network.

15. The device according to claim 1, further comprising ohmic resistors, through which a current driving the network junctions flows.

16. The device according to claim 1, further comprising a compensation circuit for producing a secondary magnetic field in such a way that the magnetic flux produced by a primary magnetic field can be compensated in at least a portion of the network cells in a controlled fashion.

17. The device according to claim 16, wherein a computer is provided for processing a voltage response of the device and the compensation circuit.

18. The device according to claim 1, further comprising a planar arrangement in such a way that the magnetic flux produced by a primary magnetic field in the planar arrangement is coupled into at least a portion of the cells of the network.

19. The device according to claim 1, further comprising a compensation circuit for producing a secondary magnetic field in such a way that a controllable magnetic field can be produced at the location of at least a portion of the network cells.

20. The device according to claim 19, wherein a computer is provided for processing a voltage response of the device and the compensation circuit.

21. The device according to claim 1, wherein a computer is provided for processing a voltage response of the device.